Share this story

What is the first indication of skin cancer? An odd-looking mole on the skin. How about cervical cancer? We search for cells that look abnormal. The eyeball, whether aided by microscopes or not, has a critical role to play in medicine, since it feeds information to a brain that is very good at picking out subtle differences.

This is why endoscopes are so useful: they allow doctors to see what would otherwise be hidden. But even then, most endoscopes only show the surface features of organs, while a good diagnosis requires looking at cells that are hidden beneath the surface. This is exactly the problem that a large group of scientists, doctors, and engineers has addressed. The researchers have developed an endoscope that is much better at revealing hidden features.

Water is transparent

In some ways, we should be surprised that we cannot see beneath the surface of our skin. If you’ve ever looked at cells under a microscope, it is really hard to make anything out. You see a couple of thin, barely visible membranes and a few mostly transparent lumps. A cell is mostly water, and most of the light simply passes through it.

Unfortunately, those barely visible parts are enough to change the direction of any light that does pass through, making the next layer blurry. If there were only two layers, you might overcome the blurriness. But there are thousands of layers, each contributing its own distortion, leaving you with a white haze.

At the level of physics, each photon has its direction changed slightly every time it passes through a membrane or bounces off a vesicle. As a result, a reflected photon travels by a random path into the tissue and back out. The randomness of the path is a blessing and a curse: the photon carries some of the path information with it, but interpreting the information is very difficult, and this prevents an image from being reconstructed.

You can see this effect yourself by putting your hand over a bright light. Your fingers will start to glow from the light that passes through the tissue, but the image of the filament is lost by the random path the light takes through your hand.

Labeling photons

But imagine that you could put a tag on each photon—we won’t go into how you do this, because you can’t, though there is a way to label groups of photons. Photons Anna, Bill, and Celine are sent into the tissue, and we time how long they are away for. Bill might return first, followed by Anna, while Celine drags in last having spent her time on a photonic pub crawl.

Now, given the travel time and an idea of the average properties of the material the light traveled through (water, in our case), we can compute the distance that Bill, Anna, and Celine traveled.

An image can be reconstructed by doing that for billions more photons. You carefully keep the illumination conditions the same and measure photons exiting from different locations of tissue.

Once these measurements are combined, an image can be created in various ways. Essentially, image reconstruction requires that all photons have scattered through the same volume, and, therefore, all photon trajectories can be explained by the properties of that volume. A sort of reverse-search of possible volumes reveals the most-likely 3D structure of the volume.

This imaging technique is called optical coherence tomography.

Old new and new news

Optical coherence tomography is old, and it has even been used in endoscopes. But the images tend to be quite blurry. The problem is basically how to squeeze everything into a tube that’s small enough to send inside a human, all while keeping the quality of the optics high.

The issue is that all lenses have imperfections, called aberrations, even if the fabrication is absolutely perfect. Typically, the smaller the lens, the larger the effect of the aberration. In terms of optical coherence tomography, this means that we blur the point where we sample photons. As a result, the quality of the image goes down.

The researchers created a 2D metamaterial that basically consists of rings of pillars. The diameter and spacing of the pillars modifies the optical properties of the surface locally. Effectively, the light emitted from each ring mixes with the light from all the other rings. The mixing can result in constructive interference (a bright spot) or destructive interference (a dark spot). The rings are structured such that at a distance of about 0.5mm, there is a single very tiny spot, just like you would get from a lens. However, this metamaterial lens is flat (like a Fresnel lens) and has been engineered to minimize many of the aberrations.

Searching for alveoli

The metamaterial-lens-equipped endoscope outperformed two other endoscopes that used more traditional optical components (a normal lens and a fiber that focuses light).

After characterizing performance, the researchers imaged a number of tissue samples, including human lung tissue (ex vivo, in this study). They showed that they could obtain relatively clear images of the epidermis, alveoli, cartilage, and blood vessels; they also picked up an abnormality that had been highlighted in the histological images. The key point being that some of these features could not even be seen in images taken with traditional endoscopes.

Some of you may be waiting for a bigger reveal—it’s science and there must be some big discovery. But there isn’t one. I know we like to talk about big breakthroughs and fundamental insights. Science and medicine don’t just advance in big jumps, though. Lots of little steps are more common. And, when you look closely, many of the big jumps involve a run up of lots of little steps.

This endoscope may be one of those little steps. The imaging improvement is not going to revolutionize anything, but it will save lives if it ends up in clinics. And it should allow research scientists to spot tissue abnormalities earlier and understand their development better. All of that makes a difference.

Share this story

Chris Lee
Chris writes for Ars Technica's science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He Lives and works in Eindhoven, the Netherlands. Emailchris.lee@arstechnica.com

54 Reader Comments

Having had an endoscopy, I am glad I didn't see what they did it with. I was night night in sleepy land.

That's of course what happened to me too (I clicked off like a light switch out in the hallway), but for some reason I hallucinated/dreamed getting off the gurney, walking into an operating room, and laying on the table. The memory is really vivid. General Anesthesia is a hell of a thing.

The actual procedure is nothing, but the prep is SO grim. Apparently they've changed the formulation again so it's less gross to administer (the liquid I took can best be described as "artificially sweetened death in a little bottle"), but the effect ... yeah, let's not talk about this anymore.

My first surprise was here drink this stuff so you don't miss out on protein over three days. Oops, it's soy. So fast forward two days of 'results' in 45m. At least I knew for certain that soy is a problem. :-P

Last time was both ends. Yes, sedation is the ticket.

My doctor had me use an over the counter product that I mixed with Gateraid. I could use any favor that wasn't red. So the favor was OK, the end result were still unpleasant.

You probably do want it. About ten years or so, "virtual colonoscopies" were heavily advertised as more comfortable than regular ones. That fad seems to have faded, and this little claw is one of the reasons.

With a virtual colonoscopy, you can detect abnormalities, but if any are found, you still need a regular colonoscopy to remove the polyp, or to take biopsy samples.

The other reason virtual colonoscopies didn't catch on is that the main discomfort for real ones comes from the prep - and the virtual ones need more or less the same prep.

Awesome! I wonder how they reconstruct the images and if it could be furthered towards some sort of xray alternative. This sort of technology is extremely promising especially when combined with other forms of nanotech.

It is quite unlikely that this could be used for x-ray imaging, because metamaterials are harder and harder to make as wavelength is narrowed. Which is why they started being employed first for radiowaves, then microwaves, I believe they have managed some infrared wavelengths as well, and recently they started experimenting with visible light (by making structures smaller than 400 nm).

In the future they might even make UV metamaterials, but beyond UV it should be impossible because they would have to make structures below 10 nm (for soft x-rays) or even below 1 nm (for hard x-rays). Beside the immense difficulty in making structures so small (<1nm structures are impossible anyway, unless functional picotechnology was developed), these are scales where quantum mechanical effects start to dominate and refuse to play along.

Having had an endoscopy, I am glad I didn't see what they did it with. I was night night in sleepy land.

Having had both an endoscopy and a colonoscopy whilst fully conscious and watching on a monitor I can say you missed out on a fascinating journey through your insides. It's weird seeing yourself from that perspective but also interesting.

Our local centre does not like having unconscious patients for endoscopies because they say the risk of oesophagus or bowel perforation is very much increased. My wife was very unhappy about this but as I pointed out to her, given that there was nothing found to be wrong, had she had a perforation she would have been still more unhappy.

To pluck polyps out of your intestine. It's the worst "happy 50th birthday" present ever, but very, very effective.

Polyp plucking is usually a good thing. Polyps are nearly always benign or pre-cancerous, so snipping them while they're still polyps prevents potentially REALLY bad birthdays a few years down the road - or possibly an abrupt end to them altogether.

That said, while I would want painkiller, I do NOT want the memory erasing drug. I mean, if it's going to hurt, it's going to hurt. Those moments, that agony, happened whether I remember it or not. All preventing me from remembering it benefits is the doctors.

My sister was not pleased at how long it took her to recover from the heavy sedation of her first colonoscopy, so on her second, demanded the lightest possible anesthesia. As she was not only slower to recover, but now has some very painful memories, she will be returning to plan A for the next. With several 1st degree relatives dying of colon cancer, our family have plenty of opportunities to do that experiment if we so wish. But since she has already done it for us, none of the rest of the family seems keen to see if her experience was a fluke.

I've only experienced one of theses procedures. They gave me atIvan (oral) and fentanyl (inj). A bit dopey but I was actually awake for the whole thing. Prep was PEG (miralax) in lemon gatorade. For me that was the worst part. Drinking about a gallon of that nasty salty stuff.

We have come along way from "worst happy 50th birthday present" ie. colonoscopy.

The FIT(Fecal Immunochemical Test)kit works almost equally well and in some parts of the world is the recommended standard as opposed to a thoroughly unpleasant and invasive procedure.

You've got options! My doctor seemed disappointed that he had to write a referral for the FIT instead of a colonoscopy.

In Australia the government issues free fecal occult blood detection kits to anyone over age 55 (I think) and reissues them every 2 years (used to be every year). Stupidly, only about a third of the test kits are used and sent back for analysis by the recipients.

To pluck polyps out of your intestine. It's the worst "happy 50th birthday" present ever, but very, very effective.

Good god, I hate finding out so very many of the "simple procedures" that apparently hurt for reasons I don't understand have just been described euphamistically all this time to hide the true horror. Endoscope to "look at your intestines"? Yeah, didn't really have a clear underestanding of why that was so painful. Giant metal teeth from a nightmare bot biting chunks off inside of you? Yeah, now I get it.

It's not painful, even if you're one of those crazy people who want to be awake for it. The stuff you have to do beforehand to clear the pipes is beyond terrible, though.

To pluck polyps out of your intestine. It's the worst "happy 50th birthday" present ever, but very, very effective.

Polyp plucking is usually a good thing. Polyps are nearly always benign or pre-cancerous, so snipping them while they're still polyps prevents potentially REALLY bad birthdays a few years down the road - or possibly an abrupt end to them altogether.

Absolutely! As gross as the whole thing is, please everybody, DO IT when it's time.

The scope procedure is uncomfortable as your colon needs to be inflated to allow proper examination. You will be passing large amounts of gas while having it done and afterwards. The scopes are getting smaller and there's always the option of using a paediatric or oesophagogastric scope if a normal colonoscope is too large.

The prep is unpleasant, though. Unfortunately it's necessary to ensure that everything that needs to be seen _can_ be seen. One thing to keep in mind is that these are "bowel cleansers" rather than laxatives; they're extremely effective if taken correctly and it's important to follow all the instructions, especially about ensuring adequate fluid intake. I read somewhere that putting a little Vaseline around the anus will help prevent soreness, but do it before you take the bowel prep! All that as said, please do not put off having this test if your doctor recommends it; no-one is going to tell you it's a fun way to spend a day, but if there's anything untoward going on in the bowel it's far better to find it early and get it removed ASAP.

FWIW, I work on the admin side of this for part of my day job with the prospect of the doctors I work for seeing an entirely new side to me, i.e. the backside, in the near future. Can't say as I'm looking forward having my colon treated like a blocked sink but the alternative is possibly something unpleasant, even fatal, at some point in the future.

More than a couple of the doctors refer to having scopes at both ends as a "spit-roast", BTW.

(Edit: phone keyboard is not working well this evening!)

I'd much rather have the spit-roast as compared to a rigid cystoscopy, which my doctor referred to as the "Metal Stallion". A long inflexible rod of metal is NOT meant to go places where it was sent.

I've had the first twice, and the last once...and that was certainly enough.

Having had an endoscopy, I am glad I didn't see what they did it with. I was night night in sleepy land.

That's of course what happened to me too (I clicked off like a light switch out in the hallway), but for some reason I hallucinated/dreamed getting off the gurney, walking into an operating room, and laying on the table. The memory is really vivid. General Anesthesia is a hell of a thing.

The actual procedure is nothing, but the prep is SO grim. Apparently they've changed the formulation again so it's less gross to administer (the liquid I took can best be described as "artificially sweetened death in a little bottle"), but the effect ... yeah, let's not talk about this anymore.

Interesting, when they did mine they sent me to lala land with injected valium.

Cool! As a camera and lens aficionado have been speculating about the potential use of metamaterials for optics since I first heard of them. Imagine a 10-1000mm zoom that would cover a full frame sensor that was no bigger than a small 50mm normal.

You still have the issue of aperture size though. Can't get around that.

You might be able to engineer something very compact, but a 1000mm lens that is 1mm in diameter is still going to be an f/1000 lens, which isn't going to be very useful. A metamaterial lens can't magically grab photons which aren't incident upon it.

Now maybe someone can make a very wide focal range zoom lens that also acts as a photomultiplier...

Nightvision is also one of those areas I am intrigued about with metamaterials and such. Can we make "passive" photomultipliers that can stand up to wide lighting conditions and are adaptive? Even though I just had laser eye surgery done, I'd be willing to dip my toes in to contact lenses again if I could get a pair that can adapt to lighting conditions and provide a few (or a few dozen) times light enhancement for better nightvision. Granted, for those starless night settings you really need like 1,000,000 light enhancement, but 100x would still make an enormous difference in nighttime visual acuity.

To pluck polyps out of your intestine. It's the worst "happy 50th birthday" present ever, but very, very effective.

Polyp plucking is usually a good thing. Polyps are nearly always benign or pre-cancerous, so snipping them while they're still polyps prevents potentially REALLY bad birthdays a few years down the road - or possibly an abrupt end to them altogether.

That said, while I would want painkiller, I do NOT want the memory erasing drug. I mean, if it's going to hurt, it's going to hurt. Those moments, that agony, happened whether I remember it or not. All preventing me from remembering it benefits is the doctors.

My sister was not pleased at how long it took her to recover from the heavy sedation of her first colonoscopy, so on her second, demanded the lightest possible anesthesia. As she was not only slower to recover, but now has some very painful memories, she will be returning to plan A for the next. With several 1st degree relatives dying of colon cancer, our family have plenty of opportunities to do that experiment if we so wish. But since she has already done it for us, none of the rest of the family seems keen to see if her experience was a fluke.

I'm perfectly fine being actually out cold. I'm less thrilled with experience pain and terror and then just not remembering that I did later. How does that benefit me? So yea, I'm really not sure how stuff like that got past ethical review.